Earned income is NOT capital gain/loss. Earned income is NOT business income.
Business income is only applicable with an entity. FWIW, a sole proprietorship qualifies as an entity for this purpose. But caution is warranted as a sole prop since capital gain/loss is reported on IRS forms other than Schedule C... no income/revenue from trading is shown on Schedule C, which may cause IRS scrutiny. Footnotes are necessary. Seek professional guidance such as Green.
The trading account MUST be in the name of the entity. If the entity qualifies for TTS, the entity can make an MTM election. If the entity does not qualify for TTS, election of MTM is meaningless, as without TTS, trading income/revenue will not be recognized as ordinary anything by the IRS... It's cap gain/loss and that's that.
If the entity is treated as an S-Corp for tax purposes, business income (trading income/revenue = ordinary business income) can be paid as wages, which includes payroll deductions. Those wages of course are earned income to the employee.
An S-Corp files form 1120s at tax time.
Employees receive a W-2.
Shareholders receive a K-1.
Here's a working version of the link someone else posted.
https://greentradertax.com/how-to-be-eligible-for-substantial-tax-savings-as-a-trader/
HTH